In one embodiment, a semiconductor manufacturing system includes a film forming apparatus configured to form a film on a surface of a wafer. The system further includes a gas supply module configured to supply at least a type of source gas for the film into the film forming apparatus. The system further includes a measurement module configured to measure a discharge amount of an exhaust gas from the film forming apparatus. The system further includes a controller configured to calculate a value corresponding to a surface area of the wafer based on the discharge amount of the exhaust gas from the film forming apparatus, and to control a supply amount of the source gas to the film forming apparatus based on the value corresponding to the surface area of the wafer.